Update to assertj-core 3.26.3

Closes gh-1706

dependencies/spring-authorization-server-dependencies.gradle

@@ -16,7 +16,7 @@ dependencies {
 		api "org.bouncycastle:bcpkix-jdk18on:1.78.1"
 		api "org.bouncycastle:bcprov-jdk18on:1.78.1"
 		api "org.junit.jupiter:junit-jupiter:5.11.0"
-		api "org.assertj:assertj-core:3.25.3"
+		api "org.assertj:assertj-core:3.26.3"
 		api "org.mockito:mockito-core:4.11.0"
 		api "com.squareup.okhttp3:mockwebserver:4.12.0"
 		api "com.squareup.okhttp3:okhttp:4.12.0"